Commuting with Panniers - which side?

Just got a bargain on a rack and bags for stuffing my pants and packed lunch in for getting to work. Delighted to be finally getting away from backpacks and courier bags.

Rarely am I going to need both bags so on a normal day which side would folk recommend if only one is in use? I think I've heard arguments for keeping away from the drivetrain grime and also argumnets for putting the bag on that side to ward away motors, but what are peoples experiences/thoughts?

WhI had panniers, I always used the drivetrain side to give me more bulk and reflective stuff for the idiots in cars. HOwever it can cause a bit of imbalance, more noticeable when wheeling the bike around, I've no got a rack bag as I only need to carry sarnies, and a couple of tools really.

Mine's on the left, but that's because the R/H one's on Mrs BigJohn's shopper, and that's the one that the Balti got spilt in during a drunken run home from the curry house with a takeaway, after the pub.

I've always split the load between two whether I need the room or not. I tend to keep the things I hope not to need like tools tubes and waterproofs in one and the food and clothes in the other. Also you may need to carry home more than you take in (think Johhny Cash - One Piece At A Time). It's also the best way to make the bike look wider to traffic.